From bud to berry, with special reference to inflorescence and bunch morphology in Vitis vinifera L.

A brief review of the reproductive system of the grapevine is presented. Phases discussed include floral induction and initiation during early spring, inflorescence primordium growth during summer to dormancy, flower formation at budburst in the subsequent growing season, and finally flowering and berry development. Difficulties in clearly defining and describing some of these developmental stages will be outlined, especially the complex bud system, the morphology of buds at budburst, and the course of flowering. The course of floral development during dormancy and at the time of budburst requires further attention, especially the reported effect that low temperature at budburst leads to increased numbers of flowers. Also, the recent finding that ‘intercarpellar’ floral organs can be induced by applying auxin is of particular interest and will be described. Case studies from Burgundy vineyards with Chardonnay, Pinot Noir and Gamay ovaries and berries will be included. A detailed analysis of what constitutes a grape bunch will be presented from observations of Chardonnay inflorescences and bunches collected at random after set and at harvest in two seasons from spur-pruned, cane-pruned and hedged vines growing on two sites varying in climate and productivity (Adelaide Hills and Southern Vales of South Australia). This analysis covered variability in numbers of branches and flowers and in per cent berry set, as well as relationships between branch numbers and flower numbers. Relationships between flower numbers and per cent set, per cent set and berry size along the inflorescence, and berry size and seed complement are outlined. Likely implications of inter-bunch and intra-bunch variability for bunch compactness, berry composition and yield components are discussed.